Motor-control system.



J. D, lHLDER.

MOTOR CONTROL SYSTEM. APPLICATION FILED JULY 22. I915.

Patented E90. 17, 1918.

2 SHEETS-SHEET I.

WITNESSES: 7 324, C i m IITW J. D. IHLDER.

MOTOR CONTROL SYSTEM. APPLICATION H LED JULY 22,1915. 1,288 418. Patented Dec. 17,1918.

2 SHEETS-SHEET 2- I I f WITNESSES. I l/Vl/EA/TOR UNITED STATES PATENT orrrcn.

JOHN D. IHLDER, OF NEW YORK, N. Y., ASSIGNOR TO OTIS ELEVATOR COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

MOTOR-CONTROL SYSTEM.

Specification Letters Patent.

Patented Dec, 17, 1918.

Application filed July 22, 1915. Serial No. 41,224.

. ful Improvement in Motor-Control Systems,

of which the following is a specification.

My invention relates in general to the control of electric motors, and is directed more particularly to the electric motors used in operating elevators and the like.

The object of the invention is to provide means whereby the motor may be operated economically and controlled in a practical and most ei'ficient manner, so that the elevator or other appliance connected with the motor will operate with an unusually high degree of economy and safety under all possible operating conditions, and to these ends my invention consists in the features of construction and arrangement having the mode of operation substantially as hereinafter more particularly pointed out.

in the accompanying drawings, Figure 1 represents a direct drive or traction elevator insta ation containing an embodiment of i 2 is a diagrammatic repiny inverter a resentation of various electric circuits;

3 and l are modifications.

characters ofireierence denote similar parts in all of figures.

prevailing types of electric direct drive traction or gearless elevator stands foremost, for not only is particul y well adapted to the present day for rise at hi h speed, but it also possesses an unusually h h efliciency a mechanical standpoint L1 the p'ower cetween motor transmission oi I 'l '4' W a and the load is a rest and no consequence 1 i 1 r nsr-iission tosses are low and tr 3 stati st is a a w i 's w oi mile u i/ W, t

ossity he or lower 'l 1 J. '1 .z Cwllly t0 0 t relieving a cl with substantially out-pot.

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should not be permitted. to exceed a predetermined amount even with load conditions which constantly vary and whichmay be either positive or negative in character. In order to attain this result with any degree of satisfaction, it is the prevailing practice to' design the motor so that the ohmic resistance of its armature shall be low, since it is well known that in order that a shunt motor may be substantially self-regulating for changes in load, particular attention must be directed to the resistance ofthe armature winding. With a self-regulating shunt motor of low armature resistance, it is customaryvto carry the field magnetization fairly high to the limit that the full load starting current shall not exceed the full load running current, and while this arrangement makes for high etficiency at full running speed of the motor, the consumption of power at starting, stopping and also on slow speed runnmg is very stopped in its usual operation at frequent inr p l tervals, the motor wi requently not attain iull speed before it is stopped again, or best will not operate at full: running speed for any appreciablelength of time and hence one derives no great benefit from the high running ei ioien cy and. in consequence the average or total einciencv is low which, or cours means a substantial waste of power. According to my invention, I arrange the otor to run on a neld magnetization so low t at may be varied within sufiicient linei o the power consumption in starting, acce and slow speed running I the same as that required for i 14 over the same distance of c e'l arm in manner l avoid the vy on sumption of power which inva- Ly occurs, when the speed of the motor is controlled by external resistances.

iorm acceleration of a fflfiijlln" less elevator machine, the field magnetization must-be doubled in starting and accelcrating to allow the motor during this period to run on half speedrunning current, consuming'the same power that would be used in covering the same distance at full speed at double current, and for friction and other losses which vary for every machine and hatchway installation an additional margin in thefield magnetization has'to be allowed in order'to keep the current to this proportion. Under usual conditions a gearless traction machine will require a variation of 21}- :1 for it field magnetization. A motor of this design permits also of running on a proportional reduction of speed without waste of power. To build a motor along these lines necessitates increasing the size over the one which is designed for small surplus of starting magnetization and high full speed running efficiency. When it is necessary to make the great saving in power consumption and efliciency in starting, slowspeed running, acceleration to full speed and stopping without materially increasing the size as well as the cost of the motor, I employ an unusual large number of turns of armature winding with resultant increase in the armature resistance. This increased reslstance results in loss in full speed running efhclency and speed variation, the efiiciency lossamounting to a few per cent. at most is of very small importance in comparison with the great gain made at starting, accelerating and slow speed running. In order to overcome'the speed variation, I provide two reverse-series field windings, one being active on the up motion of the elevator car and the other wlnding being active on 'thedown motion of the'car, it being well known that a variation of speed of-an electric motor due to variations of load may be compensated by means of a reverse series winding of the required strength. The mechanical efliciency of an elevator installation depends in a large degree upon the weight of the counterbalance relatively to that of the car and load, and good practice decrees that the preponderance of weight on the side of the counterbalance should be somewhat less than one half of the full load and the car. With this preferred arrangement of ounterbalance, the increase of speed with full load on the down motion will exceed the increase in speed with the empty car going up, while the decrease of speed with the empty car going down will be less than the decrease of speed with full load going up, but since it is generally permissible to allow considerable decrease, of speed for a full load going up, it is very undesirable to permit an increase of speed with a full load going down. To enable me to control the permissible variation in speed for the up and down motions, I use a reverse field "H of the reverse series winding winding arranged to give a difierent magnetizing power for the up and down motions of the elevator. This result may be attained in several ways, one of which is shown in Fig'. 2, and comprises two independent reverse field windings so connected and arranged that'but one of them is active at a time. Thi independent action is important since on the up motion it may be permissible to allow a considerable reduction of speed with full load, and the empty car going up represents less than full load counterbalance, hence on the up motion the reverse series winding on the motor may be and preferably is provided with less turns than that used for the down motion.

Other ways of accomplishing a similar re sult are shown in Figs. 3 and 4, in which the reverse field comprises a single winding with one or more parallel resistances.

Referring to the drawings, Fig. 1 represents a typical direct drive or gearless traction elevator comprising an elevator car B and counterbalance weight W which are suspended from opposite ends of the cables B, the latter being driven by frictional engagement with a grooved sheave E rotating with the armature of an electric motor M. A

controlling switch D within the car is connected by flexible conductors to a controller C containing the various switches, etc., for

controlling the motor circuits. These-circonnected in the armature circuit of the motor. The operation of the system of control may readily be seen by following out the various circuits.

Assumin the operator in the car moves the lever of switch Din a left hand direction so as to engage the switch contact 4, a circuit is thereupon closed to the magnet winding of the reversing switch R and the latter at once closes the proper motor circuits to cause the elevator car to ascend. The motor 7 circuits may be traced from the main, through the contacts -5 of switch R, to conductor 6, through the contacts 7 of switch R, to and through the motor armature by way of the brushes 8 and 9, through the part contacts 10 of the switch R, and by way of the conductor 11, through the series field winding S and starting resistance J' tothe --min.

The shunt field G and extra field K are energized concurrently with the motor armature and receive current directly from the mains, an adjustable resistance L being in series with the extra field winding whereby its magnetizing'power may be suitably regulated and controlled. The motor now starts. The operator-in the car next moves the car switch lever farther to the left into engagement with the contact 17 which connects the accelerating magnet A in shunt to the armature brushes. As the motor accelerates toslow, speed its counter-electro-motive-force rises, and the accelerating magnet operates successively to close the contacts 1, 2 and 3, in the order named to short circuit the starting resistance J and finally the series field winding S, and the motor runs up to normal slow speed, its field magnetization at this time being that due to the resultant action of the shunt field winding, re-

verse field winding H, and the extra field winding K. The motor may run indefinitely at this reduced speed with high field magnetization and high eificiency with a current consumption of substantially one half of that required for full speed running with the same load. The operator in the car next moves the car switch lever farther to the left into engagement with the contact 12 which causes the magnet switch F to operate and open its contacts 14 and thereby open-circuit the extra field K in one or more steps and the motor runs up to full running speed with the shunt and reverse series field tor, andtaking current from the mains, the

reverse series winding tends to weaken the total field magnetization to increase the speed, while on the other hand if the motor be driven by the load as a generator the current in the reverse series winding will act cumulatively to assist the shunt field winding, thereby increasing the total field magnetization and reducing the speed.

If the operator wishes to descend, the car switch is moved in a right hand direction so as to operate the reversing switch R and thereby close a circuit through the lower contacts of the reversing switch R to the motor, the motor armature circuit now being in a direction reverse to what it was before. Upon tracing this circuit, it will be found that the part I of the reverse series windin is now active while the part H of this win ing is dead, being open-circuited at the contacts 10 of the reversing switch It. The compensating action due to the reverse series winding I is precisely like that of the winding H, but since the part I contains more turns of winding than the part H, the compensating action of the reverse series is more marked in the case of a descending car than in the case of an ascending car, which action is purposely so arranged and from the stand-point of safety is of great importance.

In Fig. 3, the reverse series winding T is connected so as to have full power on the down motion of the car, with the reversing switch R in raised position, whereas on the up motion of the car with the switch R in raised position, the resistance 0 is connected in parallel, or as a shunt to the reverse field winding T by means of the additional contact 15 of the reversing switch R, hence only a portion of the armature current flows in the reverse winding. With this arrangement, the turns of reverse field winding are more eflective on the down motion than on the up motion. I

In Fig. 4, both of the reversing switches are provided with additional contacts, such as 15 and 16, controlling resistances O and P, respectively, the resistance 0 being of usuall field S since it is most efi'ective to keep down the starting current and to counteract in starting the demagnetizing effect of the reverse series winding. Obviously my lnvention is equally well adapted to any standard or s ecial type of shunt, compound or three win ing e ectric motor.

What I claim is 1. An electric elevator comprising a differentially wound electric motor operable at normal speed with low field magnetization, the series field winding acting always difi'erentially to the shunt-winding of the motor while the latter isacting as a motor,

and cumulatively with the said shunt wind ing when the motor is acting as a generator, and means to vary the speed of the motor and increase the starting torque by increasing the motor, field magnetization.

2. 'A traction elevator comprising a slow,- speed electric motor operable at normal speed with low field magnetization, a diiferential field winding on the motor for maintaining a substantially uniform speed with portions of one of the said windings in ac-.

varying loads, and an extra field winding for effecting a reduction in the speed of the motor by increasing the field magnetlzation.

3. An electric elevator comprising an electric motor, a controller for efiecting uniform acceleration of the motor, said motor operable at normal speed with low field magnetization, and means to increase the field of the said windings in accordance with the direction of rotation of the motor, said magnetizing power opposing that of the other winding When starting the motor in either direction.

6. An electric motor comprising difierentially wound speed compensating windings, and means for rendering active difi'erent cordance with the direction of rotation of the motor armature.

7. The combination with an electric motor havindg a field winding, of a reverse serles fiel winding therefor, and means for rendering active more or less of the turns of said series field winding according to the direction of rotation of the motor armature.

8. The combination with an electric motor having a shunt field winding, of a series field winding arranged to oppose said shunt field winding, and means for varying the number of active ampere-turns of said series winding according to the direction of rotation of the motor armature.

9. The combination with .a difierentially wound electric motor, means for reversing the motor, and means controlled by said motor-reversing means for efi'ecting the magnetization of difierent sections of one of the windings independently.

10. The combination with an electric motor having a shunt field winding, of a reverse winding on the motor field, a motor reversing switch, and means for varying the active turns of said reverse winding in accordance with the position of said switch.

11.. "The combination with an electric motor having a shunt 'field winding, of a reverse winding on the motor field comprising two portions having an unequal number of turns, and a motor reversing switch adapted alternately to energize said portions of re-- verse winding.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

JQI-IN D. II-EDER.

RUDOLPH C. SMITH, Jr. 

